The invention consists of a portable data carrying device containing a control unit and an additional data memory, each of which is implemented as a integrated circuit. The control unit is provided with means for making connection with an external read/write unit.
Data exchange and data processing systems with a multiple of such portable data carrying devices are well known. The data carrying devices are interconnected as needed for individual uses with a read/write unit in order to communicate With the system. The data carrying devices of the referenced type, which are equipped with a control unit in addition to a sufficient memory capacity, make possible not only an interactive data and signal exchange with the system, but also decentralized data processing and storage in the individual "intelligent" data carrying devices. Such data carrying devices result in extremely versatile and highly developed application possibilities. Such data carrying devices are typically put to use in card form (in credit card format with embedded integrated circuit architecture (so-called "chip cards"). Accordingly, although the data carriers are predominantly referred to hereinafter as "cards", other embodiments should nonetheless not be excluded.
In practically all applications of such data exchange systems one of the most important prerequisites is the security against manipulation and misuse or unauthorized access to the stored and transmitted information, indeed with the "fixed" system components as well as the transportable data carriers. High security requirements exist for the latter in particular on account of their wide distribution (possibility of loss or theft), but also--with "built-in intelligence"--on account of the voluminous stored data therein as well as the stored electronic encoding, as these are necessary for the protected data communication with read/write units (identification and authentication functions).